1. Field of the Invention
The present invention relates to a positive electrode active material for lithium ion battery, a positive electrode for lithium ion battery, and a lithium ion battery.
2. Description of Related Art
A lithium-containing transition metal oxide is generally used as the positive electrode active material of a lithium ion battery. Specific examples of the lithium-containing transition metal oxide include lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), and lithium manganate (LiMn2O4). The complexation of these metal oxides is undergone to improve the characteristics (high capacity, cycle characteristics, preserving characteristics, reduction in internal resistance, and rate characteristics) and safety. The characteristics different from those required for lithium ion batteries in mobile telephones and personal computers are required for lithium ion batteries used in large-sized battery applications such as car applications and road leveling applications. Particularly, high capacity and rate characteristics are regarded as important.
Various methods have been used to attain high capacity and to improve the rate characteristics. For example, Patent document 1 discloses a lithium battery positive electrode made of a complex oxide represented by the general formula LiwNixCoyAlzO2 (wherein w=0.90 to 1.10, x=0.80 to 0.95, y=0.04 to 0.19, z=0.01 to 0.16, and x+y+z=1.0) and also describes that a lithium battery positive electrode material, which has a large discharged capacity, is reduced in the deteriorations of battery characteristics caused by repetitive charge/discharge, is superior in cycle characteristics, is limited in the generation of gas caused by the decomposition of a positive electrode material after charged, and improved in preservability/safety, can be provided.
Also, Patent document 2 discloses a complex oxide represented by the general formula AwDvNixAlyNzO2 (wherein A represents at least one type selected from alkali metals, D represents at least one type selected from Mg and B, N represents at least one type selected from Si, Ca, Cu, P, In, Sn, Mo, Nb, Y, Bi, and Ga, w, v, x, y, and z respectively denote a number given by the following formulae: 0.05≦w≦1.2, 0.001≦v≦0.2, 0.5≦x≦0.9, 0.1<y≦0.5, and 0.001≦z≦0.2) as a positive electrode active material in a battery which comprises a negative electrode, a positive electrode, and a nonaqueous electrolyte including a lithium salt and can be plurally charged/discharged reversively. Patent document 2 also describes that this oxide enables a secondary battery positive electrode material to excel in all battery characteristics such as high capacitization, long life, rate characteristics, high-temperature characteristics, and safety.
(Patent document 1) Japanese Patent Application Publication No. 10-321224
(Patent document 2) Japanese Patent Application Publication No. 10-208744